1. Field of the Invention
The present invention is related to a cooling fan, and more particularly to a dustproof cooling fan.
2. Description of Related Art
A micro cooling fan is generally assembled on an electronic element which will generate a lot of heat, such as a CPU or a video-display adapter etc., to reduce the temperature of the element. With reference to FIG. 5, a conventional cooling fan has a housing (50), a stator (52) and a rotator (60) coaxially received in the housing (50).
The housing (50) has a bottom plate (51) and a flange (511) with an opening formed at the center of the bottom plate (51). The stator (52) has a sleeve (53) inserted through the opening in the flange (511). An upper pole sheet (54), a coil (55), a lower pole sheet (56) and a circuit board (57) are in turn and coaxially provided outside the sleeve (53). An oil-retaining bearing (58) is provided in the sleeve (53).
The rotator (60) has a cap (61) covering the stator (52). A ring-like permanent magnet (63) is secured on an inner wall of the cap (61) and a bushing (62) is provided between the permanent magnet (63) and the cap (61). A spindle (64) is formed at the center of the cap (61) and inserted into the oil-retaining bearing (58). A plurality of blades (not numbered) is radially formed on an outer periphery of the cap (61).
In operating, the oil-retaining bearing (58) will emit oil to lubricate the spindle (64). However, there is a gap (D) between the circuit board (57) and the cap (61), by which dust can enter into the sleeve (53) and accumulate on the oil-retaining bearing (58) and the spindle (64). The accumulated dust blocks the oil-retaining bearing (58) and the oil in the bearing (58) cannot emit out. In this case, the spindle (64) will not rotate smoothly and may even be stopped.
Therefore, the invention provides an improved cooling fan to mitigate and/or obviate the aforementioned problem.
The main objective of the invention is to provide a cooling fan which can prevent dust from entering into an oil-retaining bearing.
Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.